linux-kernel - Re: [PATCH AUTOSEL 4.14 3/4] powerpc/msi: Fix deassociation of MSI descriptors

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Message-ID: <86fsczbypl.wl-maz@kernel.org>
Date:   Wed, 28 Dec 2022 10:37:58 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Sasha Levin <sashal@...nel.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Guenter Roeck <linux@...ck-us.net>, mpe@...erman.id.au,
        christophe.leroy@...roup.eu, windhl@....com, Julia.Lawall@...ia.fr,
        joel@....id.au, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH AUTOSEL 4.14 3/4] powerpc/msi: Fix deassociation of MSI descriptors

On Tue, 27 Dec 2022 20:36:08 +0000,
Sasha Levin <sashal@...nel.org> wrote:
> 
> From: Marc Zyngier <maz@...nel.org>
> 
> [ Upstream commit 4545c6a3d6ba71747eaa984c338ddd745e56e23f ]
> 
> Since 2f2940d16823 ("genirq/msi: Remove filter from
> msi_free_descs_free_range()"), the core MSI code relies on the
> msi_desc->irq field to have been cleared before the descriptor
> can be freed, as it indicates that there is no association with
> a device anymore.
> 
> The irq domain code provides this guarantee, and so does s390,
> which is one of the two architectures not using irq domains for
> MSIs.
> 
> Powerpc, however, is missing this particular requirements,
> leading in a splat and leaked MSI descriptors.
> 
> Adding the now required irq reset to the handful of powerpc backends
> that implement MSIs fixes that particular problem.
> 
> Reported-by: Guenter Roeck <linux@...ck-us.net>
> Signed-off-by: Marc Zyngier <maz@...nel.org>
> Link: https://lore.kernel.org/r/70dab88e-6119-0c12-7c6a-61bcbe239f66@roeck-us.net
> Signed-off-by: Sasha Levin <sashal@...nel.org>
> ---
>  arch/powerpc/platforms/4xx/hsta_msi.c  | 1 +
>  arch/powerpc/platforms/cell/axon_msi.c | 1 +
>  arch/powerpc/platforms/pasemi/msi.c    | 1 +
>  arch/powerpc/sysdev/fsl_msi.c          | 1 +
>  arch/powerpc/sysdev/mpic_u3msi.c       | 1 +
>  5 files changed, 5 insertions(+)

Please drop this patch from all stable branches. It isn't needed
before 6.2, and doesn't fix anything on its own as nobody uses this
structure after this point.

	M.

-- 
Without deviation from the norm, progress is not possible.